Missing restore failure information from binlog

### Issue Description

I am trying to use a binlog file to analyze the failure as described in https://github.com/NuGet/Home/issues/9844.
However the binlog does not contain the actual error that is shown on the console:

```c#
someprojectfile.csproj(7,5): Error : System.AggregateException: One or more errors occurred. ---> System.IO.DirectoryNotFoundException: Could not find a part of the path 'c:\agent04\_work\_temp\mspdbsrv.17a37a44-6da2-4803-b51c-3e2225fc04f2\NuGetScratch\cfbbb4d423d44644b09f91277a2ef8be\adc573783fc0444ba0738b1f95891d13.proj.nuget.dgspec.json'.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
```
But instead the binlog only has the 'error': "Error Build failed".

### Steps to Reproduce

1. a solution with 218 projects in it (C++ vcxproj, C# csproj (.NET Framework) and some dotnet core projects), plus several projects using the Microsoft.Build.NoTargets Sdk and a company private MSBuild Sdk.

2. run MSBuild /t:restore /bl on the solution

### Expected Behavior

* in the case of the restore failing, the binlog should contain enough information to perform analysis

### Actual Behavior

* binlog file does not contain restore error

### Versions & Configurations

VS version : VS2019 16.5.5
OS version: Windows Server 2016 1607 (14393.3750)